1. Field of the Invention
The present invention relates to a network communication apparatus that does not include a voice communication function and that includes an ITU-T standard T.38 communication function and a function for performing communication via an IP network.
2. Description of the Related Art
In the past, for performing facsimile communication (real time facsimile communication) via the IP network, the ITU-T standard T.38 scheme for packetizing and exchanging ITU-T standard T.30 signals and the ITU-T standard G.711 (PCM) scheme for performing communications by dealing with facsimile data as voice data and the like are in practical use (refer to non-patent document 1: TTC standard JT-H323).
For performing facsimile communication by the ITU-T standard T.38 scheme, since voice ability is not essential, communication can be performed only having ability necessary for facsimile communication conforming to the ITU-T standard T.38.
In addition, in the ITU-T standard G.711 (PCM) scheme, communication can be performed by converting facsimile data to voice data and exchanging the voice data via a voice channel.
Therefore, for performing real time facsimile communications by the ITU-T standard T.38 scheme, it is only necessary to establish a facsimile communication channel. In addition, for performing real time facsimile communications by the ITU-T standard G.711 (PCM) scheme, it is only necessary to establish a voice channel.
On the other hand, in recent years, telephone conversation between a telephone terminal within an IP network and a telephone terminal connected to an analog public circuit network (PSTN: Public Switched Telephone Network) is becoming available by connecting between the IP network such as the Internet and the analog public circuit network via a VoIP (voice over IP) gateway.
The VoIP gateway has a gateway function that can be used by the ITU-T standard H.323 terminal and a SIP (Session Initiation Protocol) terminal, for example. The T.38 terminal apparatus for performing real time facsimile communication in the ITU-T standard T.38 scheme is included in H.323 terminals. Thus, by using the VoIP gateway, facsimile communications can be performed between the T.38 terminal in the IP network and the group 3 facsimile apparatus connected to the analog public circuit network.
However, when the T.38 terminal originates a call to the group 3 facsimile apparatus that is connected to the analog public circuit network, there is a case in which following problem occurs.
That is, as mentioned above, when the T.38 terminal apparatus originates a call to the group 3 facsimile apparatus, the T.38 terminal apparatus is connected to the analog public circuit network via the VoIP gateway.
In VoIP gateways currently used, there are some VoIP gateways that include the T.38 gateway function, but that report T.38 communication availability to the origination-side T.38 terminal apparatus after verifying that a destination-side terminal apparatus (PSTN side) includes the group 3 facsimile communication function.
Therefore, when the T.38 terminal apparatus originates a call to the group 3 facsimile apparatus, there is a case in which call connection cannot be properly performed according to the function of the relaying VoIP gateway, so that facsimile communication cannot be performed.